Valve gear for compound locomotive engines



Feb. 24, 1942. F. M. A. A. WALCKENAER ,9

VALVE GEAR FOR COMPOUND LOCOMOTIVE ENGINES Filed April 23, 1940 2 Sheets-Sheet 1 r- 28 R 2a Feb. 24; 1942. F. M. A. A. WALCKENAERI 2,273,913

VALVE GEAR FOR COMPOUND LOOOMOTIVE ENGINES Filed April 23, 1940 2 Sheets-Sheet? Patented Feb. 24, 1942 ENGINES Francois Marie Andre Athanase Walckenaer, Paris, France, assignorv to Schneider & Cie, Paris, France, a company of France ApplicationApril 23, 1940, Serial No. 331,228

In France July 1, 1939 Claims.

'It is known that in steam locomotives of the compound type various factors, which are still somewhat undefined, arise in practice which prevent the regulation of the admission of steam to the high-pressure and low-pressure cylinders from being that which at first View would appear to result from pure theory.

It is further known that the quantities of steam which are introduced into and exhausted from the cylinders of locomotives are governed by means of sliding valves which are automatically controlled by the rotation of the wheels of the locomotive through the use of a mechanism actuated by this rotation and comprising a suitable arrangement of countercranks, links, slotted links and transmission rods which are suitably interconnected and which impart longitudinal movement to the connecting rods of the slide valves of the high and low pressure cylinders. The control mechanism is so designed as to allow a voluntary or an automatic variation of the admission and exhaust controls.

Theoretically, the volume'of partially expanded steam to be transferred from the high-pressure cylinder to the low-pressure cylinder should always be the same since it is, in principle, equal to the total volume of the high-pressure cylinder.

Consequently, the regulation of the admission of steam to the low-pressure cylinder should be constant regardless of the condition of regulation of the admission of steam to the high-pressure cylinder. I

In actual fact, however, for various reasons and in particular owing to the retardation of the flow of the steam and the throttling thereof in the conduits, and by reason of its inertia, it is essential when modifying the admission to the high-pressure cylinder, to modify correlatively the admission to the low-pressure cylinder.

Two methods may be employed to effect this correlative modification of the regulation. According to one method, it may be left to the driver to determinewhat modification should be made in the regulation for the low-pressure cylinder for a given modification of the regulation for the high-pressure cylinder. In this case, a distribution controlling device described as having independent controls is employed.

Accordingto the other method, a connection is established between the two regulation controls so that the modification to which the regulation for the low-pressure cylinder is to be subjected automatically and necessarily results from the modification applied to the regulation for the high-pressure cylinder. For this purpose, a

mechanical connection designed and constructed to ensure the desired correlation is established between the two regulation-controlling mechanisms. In this case, it is said that the-valve gears are integrally connected. It is to this type of control that the present invention relates.

Hitherto it has, in fact, been accepted that it is sufiicient to impart to the steam supply to the low-pressure cylinder a variation to some extent parallel to that applied to the steam supply to the high-pressurecylinder, and, under these conditions, it was necessary merely to control the two variations directly and simultaneously by means of a single device conforming, for example, to that shown diagrammatically in Figure l of the accompanying drawings. However, experience has shown that the steam supply variations thus effected do not permit of obtaining an optimum output in all cases.

It has in particular been found that, in order to maintain the most favourable operation at each instant, it is necessary to impart to the steam supply to the low-pressure cylinder, variations governed by a more or less complex law.

It may especially happen that if the normal rate of admission to the high-pressure cylinder is departed from by increasing this admission, it becomes necessary to reduce the admission to the low-pressure cylinder, while conversely, if normal conditions are departed from by reducing the admission to the high-pressure cylinder it becomes necessary to increase the admission to the low-pressure cylinder and in addition, the increases and reductions in question do not always take place necessarily in accordance with linear laws.

More specifically, the invention is concerned with valve gears, for compound locomotive engines, of the type in which the mechanism for controlling the admission of steam. to the lowpressure cylinder is mechanically connected to the mechanism controlling the admission of steam to the high-pressure cylinder so as to permit the two valve gears to be controlled simultaneously from a control member which acts on a connecting rod one end of which is provided with a primary slide block movable in the usual oscillating link while the other end of said connecting rod is coupled with all the parts actuating the valves for the distribution of steam.

According to the present invention there is interposed, in the aforesaid connecting mechanism, a supplementary mechanism which comprises an auxiliary oscillating slotted link in the slot of which a secondary slide block carried by an auxiliary connecting rod is mounted, said link being coupled with the usual oscillating lever for actuating the distribution valve of the outer or low-pressure cylinder, the position of said link being adjustable by means of a link system controlled by a cam carried by the usua1 rocker whereby the aforesaid primary slideblock is controlled.

There is shown, by way of-example, in the accompanying drawings and described in the following a particular method of carrying the invention into elfect, which may be indifferently applied either to a distribution system in which the admission is controlled by the inner edges of the high-pressure slide valve and by the outer edges of the low-pressure slide valve, or to a distribution system in which the admission is effected by the inner edges for the low-pressure slide valve and for the high-pressure valve, but it will be understood that the embodiment in question could be modified in its constructional details and could be completed by any useful accessory device without departing from the scope of the invention.

In the accompanying drawings, the more or less diverse forms which have and the methods of articulation which each constructor might prefer have naturally been left out of consideration.

In these drawings,

Figure 1 shows in perspective, as hereinbefore stated, the ordinary control device having connected valve gears of known type.

Figure 2 shows, also in perspective, a device according to the invention as applied to the case where the admission is controlled by the inner edges of the high-pressure slide valve and by the outer edges of the low-pressure slide valve.

Figure 3 shows, again in perspective, the same device according to the invention as applied to a distribution system in which the admission is effected by the inner edges of the slide valves both for the low-pressure cylinder and for the high-pressure cylinder.

Figure 4 shows, in elevation, on a larger scale and partly in section on the line IV-IV of Figure 5, a detailed view of the correlation regulating cam.

Figure 5 shows the same device in plan and partly in section on the line V-V of Figure 4.

As is known and as indicated in Figures 1, 2 and 3, the periodical reciprocating movements which it is desired to impart to the connecting rods I and 2 respectively of the slide valves of the high-pressure and low-pressure cylinders are produced by means of a countercrank 3 or an eccentric which is connected to the driving gudgeon 4 and to which a control link 5 is articulated.

The control link 5 acts on an oscillating slotted link 6 movable about a fixed pin I and adapted to receive in its slot 8 a slide block 9 situated at one end of a transmission link II], the position and consequently the movements of which may be influenced as desired by the driver through the intermediary of a control rod I I acting on a rocker l2 which is movable about-a fixed pin I3 and is connected to the link III by a link I4.

The link II] at its other end is articulated at I5 to an arm I6 connected to a pin I? which is adapted to turn in bearings Iii-I8.

Also articulated to the arm IE5 at I5 is a transmission link I9 (Figure 1) which transmits to an oscillating lever the longitudinal movements of the link Ill. The oscillating lever 20 itself the different parts may connects the connecting rod 2 of the outer'slide valve to the crosshead 2| of the low-pressure cylinder, the connection with the latter bein effected through the intermediary of a link 22. Also keyed on the pin I 1 is a second arm 23 to the extremity of which is articulated a control link 24, the end 25 of which acts on an oscillating lever 26 to which are connected. on the one hand, the connecting rod I of the slide valve of the inner or high-pressure cylinder and, on the other hand, through the intermediary of a link 21, the crosshead 28 of the same cylinder.

Of course, guide slippers 29, etc., are provided in all cases where necessary.

At each turn of the locomotive wheel, that is to say, each time the driving gudgeon 4 makes a complete revolution, the oscillating slotted link 6 undergoes an oscillation and impresses a reciprocating movement on transmission link III. The magnitude of this reciprocating motion is a function of the distance separating slide block 9 and the axis of fixed pin or shaft 1 about which the link 6 oscillates. When slide block 9 is positioned near the axis of pin I, the magnitude of the reciprocating motion of transmission link I0 is small. When slide block 9 is positioned toward one of the extremities of the slot 8 in link 6, at a distance from said axis, the magnitude of the reciprocating motion of transmission link I0 is correspondingly larger. These reciprocating movements of the transmission link impress displacements on connecting rods I and 2 of the distribution valves of the high pressure and low pressure cylinders which control the periods of intake and exhaust.

As will readily be seen from Figure l, the changes in position imparted to the slide block 9 with respect to the slot 8 in the link 6 cause modifications of the movements of the admission valves in the same direction, the latter modifications remaining in a substantially constant ratio.

In the device according to the invention, of which two methods of application are shown in Figures 2 and 3, the arm I6 instead of acting directly as before through the intermediary of the link I9 on the oscillating lever 20 controlling the admission of the outer cylinder, acts on this oscillating lever through the intermediary of a link 30 articulated at 3| to one end of an auxiliary oscillating slotted link 32, which is movable about a fixed pin 33 and is intended to receive in its slot a slide block 34 on an auxiliary connecting rod 35. The rod 35 is subjected to the action of a link 36 articulated to one end of a bell-crank lever 31 which is movable about a fixed pin 38. The other end 39 of the lever 37 is connected by a transmission rod 4t (guided in fixed bearings 4|) to a roller 42 subjected to the action of a cam slot 43 connected to the rocker I2.

Owing to this device, the movements imparted to the oscillating lever 20 are a function both of the changes of position which the rocker I2 and the link I4 impart to the slide block 9 with respect to the slot 8 in the link 6, and of the changes of position which the cam slot 43, the roller 42, the rod 40, the bell-crank lever 31 and the link 36 impart to the slide block 34 with respect to the link 32.

If the cam slot 43 is suitably shaped, it is consequently possible to establish any desired relationship between the movements of the admission slide valve of the high-pressure cylinder and those of the admission slide valve of the lowpressure cylinder, both for forward and for reverse running.

Examination of Figure 3 readily shows how the change of direction of the arm 23 of the control link 24 and of the members controlling the admission to the high-pressure cylinder permits of passing from the case where the admission is efiected by the inner edges of the slide valve for one of the cylinders and by the outer edges of the slide valve for the other cylinder, to the case where the admission is effected by the inner edges of the slide valves for both cylinders.

In Figures 4 and 5, it will also be seen how the guiding and abutment of the rod 40 in its supporting bearing 4| is effected, the part 44 which ensures the abutment in question comprising a joint fitted with slight friction on the outer periphery of the part in which the cam slot 43 is out.

By means of the device according to the invention, an adaptation of distribution is mechanically obtained in a simple manner, to effeet which it would otherwise be necessary to. employ an initial phase displacement by variation of the lap of the slide valves, which initial phase displacement actually affords only a fairly narrow range of possibilities.

I claim:

1. In a valve gear for compound locomotive engines of the type embodying valve mechanisms for controlling the admission of steam to the low-pressure and high-pressure cylinders which are so mechanically connected as to permit the two mechanisms to be controlled simultaneously from a single control member which acts through a rocker on a connecting rod one end of which is provided with a primary. slide block movable in the usual oscillating link while the other end is operatively connected with the oscillating levers actuating the valves for the distribution of steam, a supplementary mechanism for correlating the movements of the low-pressure cylinder valve with those of the high-pressure cylinder valve comprising an auxiliary oscillating slotted link, a secondary slide block mounted in the slot thereof, an auxiliary connecting rod connecting said secondary slide block with the oscillating lever which actuates the distribution valve of the low-pressure cylinder, and means for adjusting the position of said secondary slide block in the slot of said auxiliary link including a cam carried by said rocker, and a link system controlled by said cam and operatively eonneeted to said auxiliary connecting rod.

2. The combination set forth in claim 1 wherein the means for adjusting the position of said secondary slide block in the slot of said auxiliary slotted link comprise a cam slot in said rocker, a transmission rod having a roller at one end thereof designed to work in said cam slot, a bell crank lever pivoted about a fixed point and articulated to the other end of said transmission rod, means for restricting the movement of said transmission rod, means for restricting the movement of said transmission rod to its axial direction, and means connecting said bell crank lever with said auxiliary connecting rod.

3. The combination set forth in claim 1 wherein the means for adjusting the position of said secondary slide block in the slot of said auxiliary slotted link comprise a cam slot in said rocker, a transmission rod, fixed bearing means wherein said transmission rod isslidably supported for axial movement only, a roller on the end of said transmission rod designed to work in said cam slot, a bell crank lever pivoted about a fixed point and articulated to the other end of said transmission rod, and means connecting said bell crank lever with said auxiliary connecting rod, said cam slot being so shaped as to provide the desired correlation between the movements of the low-pressure and high-pressure valves.

4. The combination set forth in claim 1 wherein the means for adjusting the position of said secondary slide block in the slot of said auxiliary slotted link comprise a cam slot in said rocker, a transmission rod, a fixed bearing bracket wherein said transmission rod is slidably supported for longitudinal movement only, a bearing on said bearing bracket frictionally engaging said rocker, a roller on one end of said transmission rod designed to work in said cam slot, a bell crank lever pivoted about a fixed point and articulated to the other end of said transmission rod, and a link connecting said bell crank lever with said auxiliary connecting rod.

5. The combination set forth in claim 1 wherein the means for adjusting the position ofsaid bell crank lever with said auxiliary connecting rod.

FRANQOIS MARIE ANDRE ATHANASE WALCKENAER. 

